In a piece for The Conversation, academics from the University of Western Sydney (UWS), University of Technology Sydney and University of Wollongong have tried to predict when the ideal conditions for a bush fires might kick in.

This was done by measuring the current moisture levels in “dead fuel” and “live fuel”, essentially dead leaves and sticks and living trees and plants. This was then compared to 2013 when blazes erupted in September, earlier than the start of the official bushfire season on October 1.

Fighting the bushfires at Dee Why Lagoon, in Sydney, on Sunday.Source:Supplied

The disturbing answer is that this “crucial dryness threshold” — or danger line — could be passed as early as late August, before winter has even finished.

“Our research has shown that the moisture level content of dead fuel and live fuel is even lower than it was in 2013,” Associate Professor Matthias Boer, at UWS’ Hawkesbury Institute for the Environment, told news.com.au.

“As far as fuel moisture conditions are concerned the landscape is now flammable.”

In 2017, Australia has endured its second driest June in more than a century, part of the country’s virtually rainless winter.

That has certainly been felt in Sydney. In the suburb of Richmond — on the edge of the bushfire prone Blue Mountains and Hawkesbury regions — just 0.6mm of rain fell in July compared to an average of 28.4mm.

2017 has seen Sydney’s driest winter. That leave she way open for ferocious bushfires, such as here in 2001.Source:News Limited

There were four steps, or “hurdles” that needed to be crossed for a bushfire, Prof Boer said.

The first hurdle is available fuel, such as vegetation. Secondly this has to be dry enough to be flammable, a spark is then needed to start the blaze and finally hot winds to fan it.

“The initial step has been done because there is always enough material to burn in the bush, but at this time of year it’s mostly too wet.

“But once that’s dried up the second hurdle has been passed. If you have really windy weather, like we had on Friday and the weekend, you’re getting close to meeting all the requirements for a major bush fire,” he said.

The orange bars mark the time when two significant 2013 NSW bushfires occurred. The first fires, in September, came soon after dead fuel moisture levels dipped below 10 per cent (grey line). In 2017 dead fuel moisture levels dipped below 10 per cent in early August (blue line). This isn’t good.Source:Supplied

Similarly, the moisture levels of live fuel have also reached a critical dry level earlier in 2017 than in 2013.Source:Supplied

The researchers measured the water moisture in dead leaves and twigs as well as live plants to predict when the crucial dryness thresholds would be passed compared to the dry conditions in 2013.

In that year, the moisture levels in dry fuel fell below the critical 10 per cent mark in early September. Soon after the first fires erupted.

This year, that lack of moisture threshold was reached in early August.

Similarly, the dryness of living fuel nudged the danger zone in early August this year, a month earlier than in 2013.

“The thresholds are not black and white but we have observed a strong response [in terms of fires] once thresholds are lost,” Prof Boer said.

A map of the Sydney basin accompanying the research provides further cause for concern.

Comparison of moisture levels in bushfire fuel (dead and live foliage and trees) between July 2013 and July 2017. In 2017 large splashes of orange indicate dry fuel.Source:Supplied

In 2013, much of the forested areas are coloured dark or light green. This means the foliage is still moist or transitioning from wet to dry.

But a similar map for 2017 shows large patches of orange denoting already dry and bush fire prone fuel.

Orange splashes cover much of the Blue Mountains, areas close to NSW’s third largest city of Wollongong, and parts of the northern and western fringes of Sydney.

“The orange areas are quiet abundant and are connected up. The more connected up these dry areas are, the more prone to fire propagation,” Prof Boer said.

While the map concentrates on Sydney, he said the same conditions had been recorded across large parts of NSW and the country’s wider south east.

“Much of the Sydney Basin is dangerously primed for major bushfires, at least until it receives major rainfall.

Get ready for a bad bushfire season this year. Picture: Bradley HunterSource:News Limited

“Unless we get significant rainfalls, the fuels is not likely to become wetter.”